outcome/test/tests/coroutine-support.cpp

/* Unit testing for outcomes
(C) 2013-2026 Niall Douglas <http://www.nedproductions.biz/> (6 commits)


Boost Software License - Version 1.0 - August 17th, 2003

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*/

#include <boost/outcome.hpp>
#include <boost/outcome/coroutine_support.hpp>
#include <boost/outcome/try.hpp>

#if BOOST_OUTCOME_FOUND_COROUTINE_HEADER

#include <boost/test/unit_test.hpp>
#include <boost/test/unit_test_monitor.hpp>

namespace coroutines
{
  template <class T> using eager = BOOST_OUTCOME_V2_NAMESPACE::awaitables::eager<T>;
  template <class T> using lazy = BOOST_OUTCOME_V2_NAMESPACE::awaitables::lazy<T>;
  template <class T> using generator = BOOST_OUTCOME_V2_NAMESPACE::awaitables::generator<T>;
  template <class T, class E = boost::system::error_code> using result = BOOST_OUTCOME_V2_NAMESPACE::result<T, E>;

  inline eager<result<int>> eager_int(int x) { co_return x + 1; }
  inline lazy<result<int>> lazy_int(int x) { co_return x + 1; }
  inline eager<result<int>> eager_error() { co_return boost::system::errc::not_enough_memory; }
  inline lazy<result<int>> lazy_error() { co_return boost::system::errc::not_enough_memory; }
  inline eager<result<void>> eager_void() { co_return boost::system::errc::not_enough_memory; }
  inline lazy<result<void>> lazy_void() { co_return boost::system::errc::not_enough_memory; }
  inline generator<result<int>> generator_int(int x)
  {
    co_yield x;
    co_yield x + 1;
    co_yield x + 2;
  }
  inline generator<result<int>> generator_error(int x)
  {
    co_yield x;
    co_yield x + 1;
    co_yield boost::system::errc::not_enough_memory;
  }

  template <class U, class... Args> inline eager<result<std::string>> eager_coawait(U &&f, Args... args)
  {
    BOOST_OUTCOME_CO_TRYV2(auto &&, co_await f(args...));
    co_return "hi";
  }
  template <class U, class... Args> inline lazy<result<std::string>> lazy_coawait(U &&f, Args... args)
  {
    BOOST_OUTCOME_CO_TRYV2(auto &&, co_await f(args...));
    co_return "hi";
  }

#ifndef BOOST_NO_EXCEPTIONS
  struct custom_exception_type
  {
  };
  inline lazy<result<int, boost::exception_ptr>> result_exception(boost::exception_ptr e)
  {
    boost::rethrow_exception(e);
    co_return 5;
  }

  inline lazy<BOOST_OUTCOME_V2_NAMESPACE::outcome<int>> outcome_exception(boost::exception_ptr e)
  {
    boost::rethrow_exception(e);
    co_return 5;
  }

  inline generator<BOOST_OUTCOME_V2_NAMESPACE::outcome<int>> generator_exception(boost::exception_ptr e)
  {
    co_yield 5;
    co_yield 6;
    boost::rethrow_exception(e);
  }
#endif

  inline eager<int> eager_int2(int x) { co_return x + 1; }
  inline lazy<int> lazy_int2(int x) { co_return x + 1; }
  inline eager<void> eager_void2() { co_return; }
  inline lazy<void> lazy_void2() { co_return; }
}  // namespace coroutines

BOOST_OUTCOME_AUTO_TEST_CASE(works_coroutine_eager_lazy, "Tests that results are eager and lazy awaitable")
{
  using namespace coroutines;
  auto ensure_coroutine_completed_immediately = [](auto t)
  {
    BOOST_CHECK(t.await_ready());  // must have eagerly evaluated
    return t.await_resume();       // fetch the value returned into the promise by the coroutine
  };
  auto ensure_coroutine_needs_resuming_once = [](auto t)
  {
    BOOST_CHECK(!t.await_ready());  // must not have eagerly evaluated
#if BOOST_OUTCOME_HAVE_NOOP_COROUTINE
    t.await_suspend({}).resume();  // resume execution, which sets the promise
#else
    t.await_suspend({});  // resume execution, which sets the promise
#endif
    BOOST_CHECK(t.await_ready());  // must now be ready
    return t.await_resume();       // fetch the value returned into the promise by the coroutine
  };

  // eager_int never suspends, sets promise immediately, must be able to retrieve immediately
  BOOST_CHECK(ensure_coroutine_completed_immediately(eager_int(5)).value() == 6);
  // lazy_int suspends before execution, needs resuming to set the promise
  BOOST_CHECK(ensure_coroutine_needs_resuming_once(lazy_int(5)).value() == 6);
  BOOST_CHECK(ensure_coroutine_completed_immediately(eager_error()).error() == boost::system::errc::not_enough_memory);
  BOOST_CHECK(ensure_coroutine_needs_resuming_once(lazy_error()).error() == boost::system::errc::not_enough_memory);
  BOOST_CHECK(ensure_coroutine_completed_immediately(eager_void()).error() == boost::system::errc::not_enough_memory);
  BOOST_CHECK(ensure_coroutine_needs_resuming_once(lazy_void()).error() == boost::system::errc::not_enough_memory);

  // co_await eager_int realises it has already completed, does not suspend.
  BOOST_CHECK(ensure_coroutine_completed_immediately(eager_coawait(eager_int, 5)).value() == "hi");
  // co_await lazy_int resumes the suspended coroutine.
  BOOST_CHECK(ensure_coroutine_needs_resuming_once(lazy_coawait(lazy_int, 5)).value() == "hi");

#ifndef BOOST_NO_EXCEPTIONS
  auto e = boost::copy_exception(custom_exception_type());
  BOOST_CHECK_THROW(ensure_coroutine_needs_resuming_once(result_exception(e)).value(), custom_exception_type);
  BOOST_CHECK_THROW(ensure_coroutine_needs_resuming_once(outcome_exception(e)).value(), custom_exception_type);
#endif

  BOOST_CHECK(ensure_coroutine_completed_immediately(eager_int2(5)) == 6);
  BOOST_CHECK(ensure_coroutine_needs_resuming_once(lazy_int2(5)) == 6);
  ensure_coroutine_completed_immediately(eager_void2());
  ensure_coroutine_needs_resuming_once(lazy_void2());
}

BOOST_OUTCOME_AUTO_TEST_CASE(works_coroutine_generator, "Tests that results can be generated")
{
  using namespace coroutines;
  auto check_generator = [](auto t) -> BOOST_OUTCOME_V2_NAMESPACE::outcome<int>
  {
#ifndef BOOST_NO_EXCEPTIONS
    try
#endif
    {
      int count = 0, ret = 0;
      while(t)
      {
        auto r = t();
        count++;
        if(r)
        {
          ret = r.value();
          BOOST_CHECK(ret == 4 + count);
        }
        else
        {
          BOOST_CHECK(count == 3);
          BOOST_OUTCOME_TRY(std::move(r));
        }
      }
      return ret;
    }
#ifndef BOOST_NO_EXCEPTIONS
    catch(...)
    {
      BOOST_CHECK(false);  // exception must be put into outcome, nothing must throw here
      throw;
    }
#endif
  };
  BOOST_CHECK(check_generator(generator_int(5)).value() == 7);
  BOOST_CHECK(check_generator(generator_error(5)).error() == boost::system::errc::not_enough_memory);

#ifndef BOOST_NO_EXCEPTIONS
  auto e = boost::copy_exception(custom_exception_type());
  BOOST_CHECK_THROW(check_generator(generator_exception(e)).value(), custom_exception_type);
#endif
}
#else
int main(void)
{
  return 0;
}
#endif